Web-handling device

ABSTRACT

A roller across which a flexible web moves is mounted for rotation about a longitudinal axis and is constrained for two degrees of movement, namely, pivotal movement about an upstream axis which is perpendicular to a web approach plane and also pivotal movement about an axis which is perpendicular to and intersects both the longitudinal axis and the upstream axis. This constraint can be accomplished by flexures or pivoted lengths which are connected between a roller support and a base in a manner to provide the desired degrees of movement and no others.

United States Patent Inventors John E. Morse:

Richard A. Marsh, both of Rochester, N.Y. Appl. No. 873,566 Filed Nov. 3,1969 Patented Aug. 3, 1971 Assignee Eastman Kodak Company Rochester, N.Y.

WEB-HANDLING DEVICE 6 Claims, 2 Drawing Figs.

U.S. Cl 226/21, 226/187, 226/190 Int. Cl B65h 25/26 Field of Search 226/21, 23,

[56] References Cited UNITED STATES PATENTS 3,054,547 9/1962 Alexeff 226/2 X 3,300,114 1/1967 Jacobsen... 226/21 X Primary Examiner-Richard A. Schacher Attorneys-Robert W. Hampton and Gary D. Fields ABSTRACT: A roller across which a flexible web moves is mounted for rotation about a longitudinal axis and is constrained for two degrees of movement, namely, pivotal movement about an upstream axis which is perpendicular to a web approach plane and also pivotal movement about an axis which is perpendicular to and intersects both the longitudinal axis and the upstream axis. This constraint can be accomplished by flexures or pivoted lengths which are connected between a roller support and a base in a manner to provide the desired degrees of movement and no others.

PATENTED AUG 3 |97| JOHN E. MORSE RICHARD A. MARSH INVENTORS ATTORNEYS WEB-HANDLING DEVICE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a web-handling device and more particularly to a roller which is gimbaled about one orthogonal axis and castered about another orthogonal axis upstream from the roller.

2. Description of the Prior Art Various attempts have been made in the prior art to provide guides and suitable constraints for flexible belts or webs which are fed from a supply roll to a takeup roll. Also, similar devices have been provided for endless belts. Idler rollers have been provided which are self-aligned by a belt or-web which tends to run off of one side of the roller.

One such device is disclosed in U.S. Pat. No. 2,225,276 wherein the rollers are mounted on a pivot axis which is at approximately a 45 angle to both the steering axis and the swing axis of the web. When the web tends to run to one side of this device, the roller will pivot about the pivot axis so as to drive the web back in the opposite direction.

As used in the specification and claims, the term steering axis" is an axis perpendicular to the roller axis passing through the midpoint of the roller and lying in the plane bisecting the included angle between adjacent portions of the web as it approaches and leaves the roller. The term swing axis is an axis perpendicular to both the steering axis and the roller axis and extending through the midpoint of the roller.

In a device disclosed in U.S. Pat. No. 2,653,700, a main roller is mounted in a carriage which is pivotally mounted about a vertical axis and is provided with a friction roller at the outer edge of the main roller which is engaged by the belt when it runs off the end of the roller thereby causing the carriage to be pivoted about the vertical pivot so that the main roller drives the belt back to a center position. However, neither of these devices is entirely satisfactory when used with a noncompliant belt because the tension on the belt will be uneven. Furthermore, some of the prior art systems are not very sensitive to web misalignment and must rely on a relatively gross misalignment before correction is made. Thus, the web tends to weave back and forth across the roller mechanism rather than tracking accurately. In other devices, very precise axial alignment of the tracking roller is required to avoid imposing restraints on the web. The roller must be able to pivot about the swing axis so that the tension across the web remains constant to facilitate proper tracking.

SUMMARY OFTHE INVENTION A web extending between two supports is basically a twodimensional device that lies in a single plane and therefore only has three degrees of freedom, i.e., freedom in the direction of movement, in lateral position and in angular position. Since the position of the belt in the direction of movement is indeterminate, only two of these degrees of freedom, namely the lateral position and the angular position of the belt need beconsidered. The important point in properly controlling the movement of a web is not to overconstrain or un derconstrain its lateral and angular movement. This means that exactly two constraints are needed on any web section between adjacent supports, such as an upstream lateral constraint only and a downstream lateral constraint only or an upstream lateral constraint and a downstream angular constraint.

If a web is otherwise completely constrained and must pass around a supporting roller, such as to change directions, in close proximity to a webwonstraining device, the roller must be completely decoupled from the system, that is it must not place any lateral or angular constraints on the web whatsoever. This can be accomplished by the present invention wherein a flangeless supporting roller; is mounted for rotation only about two axes in addition to its longitudinal axis. The first axis is'an upstream or castering axis which has a position which can range from being perpendicular to the approach plane of the web to being parallel to the steering axis. To determine the exact position, a number of factors must be taken into consideration, such as coefficient of friction between the web and roller, the construction of the roller, web

.width, web tension, web wrap angle around the roller w eb axes are not mutually coplanar but intersect the upstream axis' at a common pivot point. With this arrangement the first, second and third links effectively restrain the roller for castering and pivotal movement about the pivot point on the upstream axis for small displacements commonly encountered in web-handling systems. The fourth link lies in a plane common to the gimbal axis and the castering axis but does not intersect the castering axis pivot point. The fourth link, therefore, prevents rotation or lateral translation of the roller support in a plane perpendicular to the roller axis but still permits the roller support to effectively rotate about either the upstream castering axis or the gimbal axis. Rotation about the upstream castering axis decouples the roller with respect to angular web position, the absence of flanges decouples the roller with respect to lateral web position, and rotation about the gimbal axis assures even tension of the web across the surface of the roller to decouple it with respect to other downstream lateral constraints.

In an alternative embodiment wherein the support roller is.

utilized to exert a limited radial force against an anvil roller, such as a fixed-axis drive roller, the fourth link is replaced by the anvil roller which is mounted for rotation about an axis generally parallel to the longitudinal axis of the support roller to form a nip through which the web is fed. A biasing means exerts a force along a direction as previously defined for the fourth link to urge the support roller against the anvil roller to lightly grip the web in the nip.

Thus, it can be seen that the web-supporting roller device constructed in accordance with this invention has the advantage of not imposing any lateral or angular constraints on the web being supported. This advantage will become more apparent from the description which follows, taken in conjunction with the accompanying drawings. I

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of one embodiment of a web handling device constructed in accordance with this invention; and

FIG. 2 is a side elevation of a second embodiment of a webhandling device constructed in accordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with this invention, a web-handling device is provided wherein a support roller 2 is mounted on a shaft 3 for rotation about a longitudinal axis 4. Conveniently, the shaft may be joumaled in one leg 8 of a roller support S which support also includes a second leg 9 attached at a right angle to leg 8. An angle bracket 10 is also attached to leg 8. Conveniently, a web 12 approaches roller 2 along an approach plane in the direction indicated by arrow 14 and may pass around a portion thereof and leave the roller along an exit plane. The web shall be considered to be one which is both laterally and angularly constrained at the roller by means not shown. Therefore, in order to avoid overconstraining the web roller 2 must be completely decoupled from the system, i.e., it

To accomplish this, roller support S is connected in a special manner to a base B which base has been conveniently illustrated as having a vertical leg 16 and a bottom leg 18.

The web has a steering axis 20 which is perpendicular to longitudinal roller axis 4 and passes through the rollers midpoint 22 and has a swing axis 23 which is-perpendicular to both roller axis 4 and steering axis 20. Roller axis 4 is intersected at its midpoint 22 by a gimbal axis 24 which also intersects an upstream castering axis 26 at a pivot point 28. Upstream castering axis 26 has a position which can range from being perpendicular to the approach plane of the web to being parallel to the steering axis. The exact position is determined by the many factors enumerated above. To provide proper restraints on support roller 2, it must be permitted to rotate about gimbal axis 24 and upstream castering axis 26.

To accomplish this, roller support S is connected to base B by means of a number of flexures or links such as links 30, 32, 34, and 36. Each of these flexures is reduced in cross section at opposite ends thereof to provide pivot points. Conveniently, one end of link 30 is connected to bracket and the opposite end thereof is connected to a bracket 38 on leg 16 of base B. Link 30 is positioned so that the longitudinal axis 40 thereof passes through pivot point 28. A second link 32 also extends between bracket 10 and bracket 38, and has a longitudinal axis 42 also passing through pivot point 28. Third link 34 is connected to leg 9 of support S at one end and the opposite end is connected to a small angle bracket 44 on leg 18 of base 8. Third link 34 has a longitudinal axis 46 also passing through pivot point 28. It will be noted that the longitudinal axes of the first, second and third links are not coplanar.

It can be seen that for small displacements the constraint of links 30, 32, and 34 permit roller 2 to rotate about gimbal axis 24 and to rotate about pivot point 28 either in a plane which is common to longitudinal axis 4 and gimbal axis 24 or in a second plane which is common to gimbal axis 24 and upstream castering axis 26. However, it is not desired that roller 2 pivot about pivot point 28 in the second plane because support in the direction of the roller radius could not then be provided. To prevent this movement, a constraining means, such as a fourth link 36, is interconnected between leg 9 of roller support S and leg 18 of base 8 as shown. The longitudinal axis 37 of link 36 lies in the plane common to gimbal axis 24 and castering axis 26 but does not intersect pivot point 28, thus preventing any pivotal movement of the roller support S about pivot point 28 in this latter plane. Although, longitudinal axis 37 has been shown as passing through midpoint 22, it will be understood that it may pass through gimbal axis 24 at any point spaced from pivot point 28. However, link 36 will still permit rotational movement about gimbal axis 24 and rotational movement about upstream castering axis 26 in the plane which is common to longitudinal roller axis 4 and gimbal axis 24.

From this description, it can be seen that roller 2 is completely uncoupled from the system except for providing radial direction support to the web. Since the lateral and angular position of the web, where it contacts the roller, is externally constrained, any steering axis error, i.e., any error in mounting roller 2 about steering axis with respect to the direction of movement of web 14, results in lateral roller motion. This lateral roller motion causes the roller axis 4 to rotate about the steering axis so that the roller axis will be absolutely perpendicular to web movement direction, as indicated by arrow 14. Thus, roller 2 will be servoed at all times to follow the web so that it will not impose substantial lateral forces on the web. The ability of roller 2 to pivot about gimbal axis 24 assures that the tension is even across the web regardless of the downstream lateral position of the web so that no further substantial lateral forces are imposed on the web. Because of this, support roller 2 need not be precisely aligned with respect to either steering axis 20 or swing axis 23 but will align itself with the web.

An alternative embodiment is shown in FIG. 2 wherein the constraining means comprises a spring 48 which biases pressure roller 2 so that pressure roller 2 is urged against an anvil roller 50 journaled for rotation in a pair of fixed spaced supports, such as support 52. The castering action provided at pivot point 28 will automatically keep the longitudinal axis of roller 2 aligned with the axis of anvil roller 50 by movement about pivot point 28 in a plane common to longitudinal roller axis 4 and gimbal axis 24. Spring 48, on the other hand acting at the center of pressure roller 2, which roller is free to pivot about gimbal axis 24 at its center, will keep the pressure uniform across the width of roller 2. Of course, in this embodiment, it will be noted that the web 12 is wrapped around a portion of anvil roller 50 rather than around pressure roller 2.

From the foregoing, the advantages of this invention are readily apparent. A web-handling device has been provided wherein a roller is castered about an axis upstream from the midpoint of the roller so that it is automatically servoed should the roller be skewed about the steering axis with respect to the direction of movement of the web 12 so that it does not exert any substantial lateral forces on the web, but provides only perpendicular support therefor. Also, the web is free to pivot about the swing axis so that the tension thereacross remains constant to avoid imposing additional lateral forces on the web. In one embodiment, the roller supports the web and is constrained for pivotal movement about an upstream axis by a series of noncoplanar links or flexure members extending between the roller support and the base and intersecting the upstream axis at a common pivot point and by a link extending between the roller support and the base and lying in the plane of the upstream axis and the gimbal axis but not intersecting the upstream axis pivot point which latter link restrains rotational movement in the plane of the steering axis and the upstream axis. The position of the castering axis can range from being perpendicular to the approach plane of the web to being parallel to the steering axis. In an alternative embodiment this restraint is provided by an anvil roller having an axis parallel to a pressure roller urged thereagainst by biasing means, such as a spring.

The invention has been described in considerable detail with reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

We claim:

1. A web-handling device for providing perpendicular support only to a flexible web which is adapted to come into engagement with said handling device along an upstream approach plane and is adapted to leave said device along a downstream exit plane at an included angle to said approach plane, said device comprising:

a roller support;

a roller mounted on said support for rotation about a longitudinal axis and engageable by said web, said roller having a steering axis extending through the midpoint thereof perpendicular to said longitudinal axis and lying in a plane bisecting said included angle;

means mountingsaid support for only two degrees of movement; namely:

pivotal movement of said roller about an upstream castering axis having a position in a range from being perpendicular to said approach plane to being parallel to said steering axis; and

pivotal movement about a gimbal axis which intersects and is perpendicular to both said longitudinal roller axis and said castering axis.

2. A web-handling device as claimed in claim 1, wherein:

said upstream axis is substantially perpendicular to said web approach plane.

3. A web-handling device as claimed in claim 1, wherein:

said upstream axis is substantially parallel to said steering axis.

4. A web-handling device as claimed in claim 1 wherein said roller support includes:

a base;

a first link having a first end pivotally connected to said support and a second end pivotally connected to said base and having a longitudinal axis passing through said upstream axis at a pivot point;

a second link having a first end pivotally connected to said support and a second end pivotally connected to said base and having a longitudinal axis passing through said upstream axis at said pivot point;

a third link having a first end pivotally connected to said support and a second end pivotally connected to said base and having a longitudinal axis passing through said pivot point, wherein said longitudinal axes of said first, second and third links are not mutually coplanar; and

means constraining movement of said roller about said pivot point in a plane common to said upstream axis and said gimbal axis.

5. A web-handling device as claimed in claim 4 wherein said constraining means includes:

a fourth link having a first end pivotally connected to said support and a second end pivotally connected to said base and having a longitudinal axis lying in said common plane which is perpendicular to said gimbal axis at a point spaced from said pivot point.

6. A web-handling device as claimed in claim 4 wherein said constraining means includes:

an anvil roller joumaled for rotation about an axis generally parallel to said longitudinal axis of said mounted roller; and

means biasing said mounted roller toward said anvil roller for gripping said web in a nip formed by said anvil roller and said mounted roller. 

1. A web-handling device for providing perpendicular support only to a flexible web which is adapted to come into engagement with said handling device along an upstream approach plane and is adapted to leave said device along a downstream exit plane at an included angle to said approach plane, said device comprising: a roller support; a roller mounted on said support for rotation about a longitudinal axis and engageable by said web, said roller having a steering axis extending through the midpoint thereof perpendicular to said longitudinal axis and lying in a plane bisecting said included angle; means mounting said support for only two degrees of movement; namely: pivotal movement of said roller about an upstream castering axis having a position in a range from being perpendicular to said approach plane to being parallel to said steering axis; and pivotal movement about a gimbal axis which intersects and is perpendicular to both said longitudinal roller axis and said castering axis.
 2. A web-handling device as claimed in claim 1, wherein: said upstream axis is substantially perpendicular to said web approach plane.
 3. A web-handling device as claimed in claim 1, wherein: said upstream axis is substantially parallel to said steering axis.
 4. A web-handling device as claimed in claim 1 wherein said roller support includes: a base; a first link having a first end pivotally connected to said support and a second end pivotally connected to said base and having a longitudinal axis passing through said upstream axis at a pivot point; a second link having a first end pivotally connected to said support and a second end pivotally connected to said base and having a longitudinal axis passing through said upstream axis at said pivot point; a third link having a first end pivotally connected to said support and a second end pivotally connected to said base and having a longitudinal axis passing through said pivot point, wherein said longitudinal axes of said first, second and third links are not mutually coplanar; and means constraining movement of said roller about said pivot point in a plane common to said upstream axis and said gimbal axis.
 5. A web-handling device as claimed in claim 4 wherein said constraining means includes: a fourth link having a first end pivotally connected to said support and a second end pivotally connected to said base and having a longitudinal axis lying in said common plane which is perpendicular to said gimbal axis at a point spaced from said pivot point.
 6. A web-handling device as claimed in claim 4 wherein said constraining means includes: an anvil roller journaled for rotation about an axis generally parallel to said longitudinal axis of said mounted roller; and means biasing said mounted roller toward said anvil roller for gripping said web in a nip formed by said anvil roller and said mounted roller. 